Disable unsupported configuration

Author: tbkka

test/stdlib/ParseFloat16.swift

@@ -1,9 +1,12 @@
 // RUN: %target-run-simple-swift
 // REQUIRES: executable_test
 
-// Float16 is not supported on x86_64 macOS at all
+// Float16 is not supported on x86_64 macOS
 // UNSUPPORTED: CPU=x86_64 && OS=macosx
 
+// Float16 is only available in watchOS 7.0 or newer
+// UNSUPPORTED: CPU=arm64_32 && OS=watchos
+
 // TODO: Figure out why this test breaks on wasm32
 // UNSUPPORTED: CPU=wasm32